In recent years, artisans have made significant advances in fabricating and using opto-electronic integrated circuits. These improved circuits, which often contain passive and active optical devices, have found significant applications in a number of fields including optical computing and communications. The use of opto-electronic circuits in many systems can result in significant cost savings, increased circuit speeds, reduced physical size and power requirements, increased reliability, as well as other improvements. As such, those concerned with the development of photonic systems in such fields as radar, communications and computing have recognized the need for improved techniques of constructing opto-electronic circuits.
Specifically, conventional phased-array antenna systems have been successfully demonstrated for transmitting and receiving microwave energy in communication and radar systems. A phased-array antenna is an antenna with two or more driven elements. The elements are fed with a certain relative phase, and they are spaced at a certain distance, resulting in a directivity pattern or beam that exhibits gain in some directions and little or no radiation in other directions. Although phased arrays may have fixed beams, they usually contain rotatable or steerable beams. Of course, an antenna structure may be physically moved to effect beam steering, however, in a phased-array antenna, beam steering is usually accomplished by simply varying the relative signal phase being fed to the antenna elements.
Although prior art phased-array antennas have served the purpose, they have not proved entirely satisfactory for use in many microwave communication and/or radar systems. To obtain sufficient radar resolution, phased-array antennas employed with some microwave radars require that as many as a thousand antenna elements be arrayed to produce a sufficiently narrow beam. Since many long-range communication systems also require narrow antenna beams, they often have antenna arrays with hundreds of antenna elements. While the size of microwave antenna arrays having several hundred or even a thousand antenna elements can be relatively small, the signal processing circuits connected to these antenna arrays often become prohibitively large and expensive to manufacture. Thus, artisans have recognized the need for reducing the size and cost of many signal processing circuits by using an optically controlled microwave system.